When sleeping in the back yard lately, I've been using a blue ccf pad in the pocket of my BIAS DL for bottom insulation, and a wool army blanket for the top. I've been toasty into the 50s, and could probably take this into the 40's since I'm a hot sleeper.
Lightweight? No. Compressible? The blue pad is bulky, and I hate bulk. But for car camping, it's perfectly acceptable.